create, but dont register, bp2build_deps mutator

This is the bulk of the "allowlist v2" feature. It will disable bp2build
generation for modules which have transitive dependencies without a
bazel build definition.

This CL includes this mutator, but doesn't register it as a bp2build
mutator (outside of a few unit tests). This allows us to easily iterate
on completion of this feature and ensure there are no launch blockers
before we finalize the change in AOSP.

Bug: 285631638
Test: Unit tests
Change-Id: Ifb0a079c409ca19b02cafa3fab2efa0d3deebc50
diff --git a/android/mutator.go b/android/mutator.go
index 57ff1e0..3d59655 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -35,6 +35,9 @@
 // RegisterMutatorsForBazelConversion is a alternate registration pipeline for bp2build. Exported for testing.
 func RegisterMutatorsForBazelConversion(ctx *Context, preArchMutators []RegisterMutatorFunc) {
 	bp2buildMutators := append(preArchMutators, registerBp2buildConversionMutator)
+	if ctx.config.Bp2buildDepsMutator {
+		bp2buildMutators = append(bp2buildMutators, registerBp2buildDepsMutator)
+	}
 	registerMutatorsForBazelConversion(ctx, bp2buildMutators)
 }
 
@@ -226,6 +229,15 @@
 	BazelConversionPathContext
 	BaseMutatorContext
 
+	// AddDependency adds a dependency to the given module.  It returns a slice of modules for each
+	// dependency (some entries may be nil).
+	//
+	// If the mutator is parallel (see MutatorHandle.Parallel), this method will pause until the
+	// new dependencies have had the current mutator called on them.  If the mutator is not
+	// parallel this method does not affect the ordering of the current mutator pass, but will
+	// be ordered correctly for all future mutator passes.
+	AddDependency(module blueprint.Module, tag blueprint.DependencyTag, name ...string) []blueprint.Module
+
 	// CreateBazelTargetModule creates a BazelTargetModule by calling the
 	// factory method, just like in CreateModule, but also requires
 	// BazelTargetModuleProperties containing additional metadata for the
@@ -294,15 +306,6 @@
 	BaseMutatorContext
 	Bp2buildMutatorContext
 
-	// AddDependency adds a dependency to the given module.  It returns a slice of modules for each
-	// dependency (some entries may be nil).
-	//
-	// If the mutator is parallel (see MutatorHandle.Parallel), this method will pause until the
-	// new dependencies have had the current mutator called on them.  If the mutator is not
-	// parallel this method does not affect the ordering of the current mutator pass, but will
-	// be ordered correctly for all future mutator passes.
-	AddDependency(module blueprint.Module, tag blueprint.DependencyTag, name ...string) []blueprint.Module
-
 	// AddReverseDependency adds a dependency from the destination to the given module.
 	// Does not affect the ordering of the current mutator pass, but will be ordered
 	// correctly for all future mutator passes.  All reverse dependencies for a destination module are